The Spectacle Reef light, like that at Minot’s Ledge, is a simple tower of massive masonry, and this is the approved design for lighthouses exposed to very heavy strain from waves or ice.  A simpler structure, used in tranquil bays and in the less turbulent waters of the Gulf, is the “screw-pile” lighthouse, built upon a skeleton framework of iron piling, the piles having been so designed that they bore into the bed of the ocean like augers on being turned.  The “bug-light” in Boston Harbor, and the light at the entrance to Hampton Roads are familiar instances of this sort of construction.  For all their apparent lightness of construction, they are stout and seaworthy, and in their erection the builders have often had to overcome obstacles and perils offered by the sea scarcely less savage than those overcome at Minot’s Ledge.  Indeed, a lighthouse standing in its strength, perhaps rising out of a placid summer sea, or towering from a crest of rock which it seems incredible the sea should have ever swept, gives little hint to the casual observer of the struggle that brave and skilful men had to go through with before it could be erected.  The light at Tillamook Rock, near the mouth of the Columbia River, offers a striking illustration of this.  It is no slender shaft rising from a tumultuous sea, but a spacious dwelling from which springs a square tower supporting the light, the whole perched on the crest of a small rock rising precipitously from the sea to the height of some forty feet.  Yet, sturdy and secure as the lighthouse now looks, its erection was one of the hardest tasks that the board ever undertook.  So steep are the sides of Tillamook Rock that to land upon it, even in calm weather, is perilous, and the foreman of the first party that went to prepare the ground for the light was drowned in the attempt.  Only after repeated efforts were nine men successfully landed with tools and provisions.  Though only one mile from shore they made provision for a prolonged stay, built a heavy timber hut, bolting it to the rock, and began blasting away the crest of the island to prepare foundations for the new lighthouse.  High as they were above the water, the sea swept over the rock in a torrent when the storms raged.  In one tempest the hut was swept away and the men were barely able to cling to the rock until the waves moderated.  That same night an English bark went to pieces under the rock, so near that the workmen above, clinging for dear life to their precarious perch, could hear the shouts of her officers giving their commands.  A bonfire was kindled, in hope of warning the doomed sailors of their peril, but it was too late, for the ship could not be extricated from her position, and became a total wreck, with the loss of the lives of twenty of her company.  To-day a clear beam of light shines out to sea, eighteen miles from the top of Tillamook, and only the criminally careless captain can come near enough to be in any danger whatsoever.  Such is one bit of progress made in safeguarding the sea.